Laser tracking method and apparatus

ABSTRACT

A device and method for remotely positioning a device utilized to illuminate a remote target. The illuminating device is scanned until illumination is detected in the field of view of a detector sighted on the remote target. On acquisition of the illumination, the scan signals are replaced by error signals related to the departure of the detected illumination from the target sight axis and the illuminating device positioned responsively thereto.

United States Patent Cunningham et a1.

[451 Oct. 3, 1972 LASER TRACKING METHOD AND APPARATUS [72] inventors:Robert A. Cunningham, Lake Park; John T. Winkler, Orlando, both of Fla.

[73] Assignee: Martin Marietta Corporation, New

York, NY.

[22] Filed: Aug. 26, 1970 {21] Appl. N0.: 66,955

[52] US. Cl ..250/203 R, 331/94.5, 356/152 [51 1 Int. Cl. ..G01j 1/20[58] Field of Search ..356/l52, l; 244/14 L, 3.13;

[56] References Cited UNITED STATES PATENTS 3,514,608 5/1970 Whetter..250/203 R Primary Examiner-Walter Stolwein Assistant Examiner-D. C.Nelms AttorneyJulian C. Renfro and Gay Chin 7] ABSTRACT A device andmethod for remotely positioning a device utilized to illuminate a remotetarget. The illuminating device is scanned until illumination isdetected in the field of view of a detector sighted on the remotetarget. On acquisition of the illumination, the scan signals arereplaced by error signals related to the departure of the detectedillumination from the target sight axis and the illuminating devicepositioned responsively thereto.

19 Claims, 6 Drawing Figures YAW ERROR CHANNEL RELAY DRIVER ACQUIS lTlONDETECTOR DEMOD.

LR FILTER SIGNAL GENERATOR PATENTEDUET 3 I972 SHEET 1 OF 5 INVENTORSROBERT A. CUNNINGHAM JOHN T. WINKLER ATTURNEY PATENTEU OCT 3 I972 SHEET5 OF 5 INVENTORS ROBERT A. CUNNINGHAM JOHN T. WINKLER BACKGROUND OF THEINVENTION With the advent of improved and more reliable laser systemssuch as are currently available, the laser has been used with increasingfrequency in both civilian and military applications. In militaryapplications, for example, lasers may be used in weapon fire controlsystems to illuminate a remote target, the reflected energy beingutilized for tracking and/or guided missile control.

A conventional practice for illuminating a target with a laser involvesthe visual acquisition of the target through the optical system attachedto and mechanically bore-sighted with the laser illuminator. Theoperator must then manually follow the target with the optical systemwhile simultaneously positioning the laser illuminator. The need forincreased power in longrange military applications has added appreciablyto the overall size and mass of the laser and has consequently reducedthe ease and accuracy with which an operator is able to position thelaser while tracking a specific target.

The increased size and mass has additionally detracted from theportability of such illuminator systems, thereby significantlydecreasing the military usefulness of the illuminator in certain terrainand tactical situations. Furthermore, the position of the operator isrestricted to the immediate vicinity of the laser and is immediatelyrevealed when the laser illuminator is utilized in the field.

The increased size and mass of the laser remains a problem even wherethe laser is not directly connected to the optical system, but isconnected thereto by means of a servo system. Such servo systems areoften prohibitive, by reason of their mass and the required degree ofcontrol, from utilization in many tactical situations, for example,where the degree of parallax is a consideration.

One of the more promising civilian applications is in the field ofmedicine, and particularly in surgical applications where lasers arepresently being used as an extremely accurate cutting tool. In theseapplications, the surgeon must manually position both the optical systemand the laser to make extremely accurate cuts in highly delicate areas.

It is, therefore, an object of the present invention to provide a novellaser positioning method and system which obviates the abovedifficulties.

It is another object of the present invention to provide a novel methodand apparatus for designating a target to a laser illuminator.

It is still another object of the present invention to provide a novelapparatus which is lightweight, highly portable and well suited for bothtactical military and civilian applications.

It is a further object of the present invention to provide a novelmethod and apparatus for positioning a laser illuminator with increasedaccuracy and without recourse to devices, mechanical or electrical,which translate the operators pointing axis to that of the illuminator.

It is yet a further object of the present invention to provide a novelmethod and apparatus for remotely positioning a laser illuminatorwhereby the position of the operator is not revealed.

It is still a further object of the present invention to provide a novelmethod and apparatus for positioning a laser prior to the application ofother energy sources collimated with the laser used to position thesystem.

These and other objects and advantages of the present invention willbecome apparent from a perusal of the following detailed descriptionwhen read in conjunction with the accompanying drawings.

THE DRAWINGS FIG. 1 is a first pictorial representation of the laserpositioning system of the present invention;

FIG. 2 is a second pictorial representation of the laser positioningsystem of the present invention;

FIG. 3 is a functional block diagram of one embodiment of thepositioning system of FIG. 1 utilizing a continuous wave laser;

FIG. 4 is a functional block diagram of a second embodiment of thepositioning system of FIG. 1 utilizing a pulsed laser;

FIG. 5 is a functional block diagram of the signal control circuit ofthe pulse processor of FIG. 4; and

FIG. 6 is a functional block diagram of the normalizer of the pulseprocessor of FIG. 4.

DETAILED DESCRIPTION As illustrated in FIG. 1, the laser positioningsystem of the present invention comprises a positionable laserilluminator 10 which may be controlled from a remote position by anoperator ll utilizing an optical sighting device 12. The opticalsighting device may, of course, be of the hand-held type illustrated ormay comprise a helmet or other apparatus worn by the operator 1 l.

The laser illuminator 10 may include a narrow beam laser 14 mounted in aconventional manner so that the laser beam may be directed, e.g., bymounting the laser 14 on gimbals 16 or by fixedly mounting the laser 14and directing the energy therefrom onto a gimbal mounted, movable mirrorof the type schematically illustrated in FIGS. 2 and 3. A positioningsystem 18 may be provided to position the laser 14 at a desired yaw andpitch angle by applying appropriate control signals to a yaw positionmotor 20 and a pitch position motor 22, thereby causing the laser beam24 to strike a remote target 26 such as the tank illustrated in FIG. 1or the bridge illustrated in FIG. 2.

The positioning system is controlled by error signals generated by alight detector 28 carried by the optical sighting device 12. The errorsignals from the light detector 28 may be applied to the positioningsystem 18 by way of a suitable conventional communications link, such asthe electro-magnetic radio wave link illustrated schematically in FIGS.1, 2 and 4, or suitable electrical conductors as illustrated in FIG. 3.

A second illustration of the laser positioning system of the presentinvention is found in FIG. 2 where the operator l1 utilizing the opticalsighting device 12 is focused on a bridge 26. The error signalsgenerated by the light detector may then be transmitted by way of asuitable communications link to an antenna carried'by a helicopter 27 orother type of aircraft.

These error signals are then processed, it not processed in thecircuitry associated with the hand-held device prior to transmission, todirect the beam 24 of the laser 14 onto the target 26.

A first embodiment of the laser illuminator positioning system of FIG. Iis illustrated in greater detail in the functional block diagram of FIG.3. Referring now to FIG. 3, the laser illuminator includes a continuouswave laser 30 providing a laser beam 32 and a suitable interrupterapparatus 34. For example, the beam 32 may be chopped by passing itthrough an apertured disc driven at the desired rotational speed in asuitable conventional manner such as by a motor 36. The light from theback surface of the chopper is applied to a reference photodetector 42having an output signal related to the rate at which the laser beam isbeing chopped and the utilization of which will be later explained. Achopped collimated light may be used instead of a laser where extensiverange is not required. The chopped laser beam 38 may be directed onto areflecting mirror surface 40, which reflects the chopped laser beam 38.

The portion of the laser beam 38 reflected from the mirror 40 ispreferably directed onto a movable, totally reflective mirror surface 44having yaw angle and pitch angle control motors 46 and 48, respectively,connected thereto in a suitable conventional manner. The mirror 44 thusdeflects the laser beam in a direction determined by appropriate yaw andpitch motor control signals YAW and PITCH applied to the respective yawand pitch control motors 46 and 48.

The yaw and pitch motor control signals YAW and PITCH are derived in oneof the following manners depending upon the position of a mode selectrelay 50. When the relay 50 is de-energized, the positioning system isin the scan mode and the Y SCAN and P SCAN signals are derived fromoutput terminals 52 and 60 of a conventional scan signal generator 54which provides signals which generate a search pattern like the rasterof a television receiver.

The P SCAN signal from the output terminal 60 of the scan signalgenerator is applied to a terminal 62 of the relay 50. The commonterminal 61 of the relay 50 is connected by way of a pair of amplifiers98 and 102, later to be described in more detail, to an input terminal63 of a conventional summing amplifier 64 to which the output signalfrom a pitch position sensor 79 and a gyroscope 73 are also applied. Theresulting output signal PITCH from the amplifier 64 is applied to thepitch control motor 48.

In the scan" mode, the Y SCAN signal from the scan generator 54 issimilarly utilized in conjunction with a gyroscope 75 to produce theoutput signal YAW applied to the yaw control motor 46.

In the track mode, i.e., when the relay 50 is energized, the YAW andPITCH signals are derived respectively from the phase demodulated andfiltered signals P ERR and Y ERR in the error signal channels 65 and 67and are applied to the terminal 116 of the relay S0. The signal from thegyroscope is thus utilized for stabilization of the laser beam in boththe scan" and track modes.

With continued reference to FIG. 3, a portion of the circuitrycomprising the error signal channels 65 and 67 may be provided withinthe sighting device 12 of FIGS. 1 and 2. The remainder of the circuitrycomprising the error signal channels 65 and 67 may be located within thelaser illuminator assembly. It may be desirable to place most of thecircuitry in the illuminator assembly since it is important that theweight of the optical sighting device 12 be minimized. For bandwidthconsiderations, especially in the pulse laser system later to bedescribed, it may be more desirable to transmit the processed errorsignals.

With continued reference to FIG. 3, the optical sighting device 12 ofFIG. 1 is provided with both an optical sight 66 and a light detector 68in optical alignment therewith. The optical sight 66 may be any suitableconventional optical system having cross hairs or other means fordetermining the center of the field of view. The light detector 68 maybe provided with a lens 77 and an optical filter 69 and is preferably aconventional Schottky barrier type photodiode detector, for example, amodel PIN-SPOT/IO four terminal photodiode detector available fromUnited Detector Technology, P. O. Box 5251, Santa Monica, Calif, 90405.The detector 68 thereby provides four signals proportional to theintensity and position of the light striking the photodiode detector.

The signal from the upper terminal of the detector 68 relates to theposition of the light striking the detector in the upper half thereof,(hereinafter referred to as the HI signal) and may be applied to aninput terminal 70 of one of a pair of conventional high gain, low noiseamplifiers 74 for amplification. The signal from the lower terminal ofthe detector 68 relates to the position of the light striking thedetector in the lower half thereof (hereinafter referred to as the LOsignal). The amplified HI and LO output signals from the amplifiers 74may then be applied to the input terminals 76 and 78 of a conventionaldifferential amplifier 80. the output signal of which is a pitch errorsignal, P ERR, related in magnitude and sign to the algebraic differencebetween the amplified HI and LO signals.

For example, if the amplified HI signal exceeds the amplified LO signal,the pitch error signal P ERR may be a positive signal related inamplitude to the difference between the HI and LO signals from thedetector 68. However, if the amplified LO signal exceeds the amplifiedI-II signal, the differential amplifier 80 output signal P ERR is anegative signal related in amplitude to the difference between the HIand LO detector 68 output signals.

The LEFT and RIGHT signals developed respectively by the left and righthalves of the detector are similarly treated to produce a yaw errorsignal Y ERR.

In addition, conventional automatic gain control signals may be appliedto both the yaw amplifiers and pitch amplifiers from a suitableconventional automatic gain control circuit 82 in order to normalize theerror signals derived from these channels, i.e., to prevent gainvariations due to range variations.

The yaw channel is similar to the pitch channel hereinabove describedand will not be further explained.

With continued reference to FIG. 3, the four input signals to thedifferential amplifiers 80 and 81 are summed in a conventional summingcircuit 83 and the summation signal applied to an input terminal 84 of aconventional phase demodulator 86. The output signal from the phasedemodulator 86 is applied to an input terminal 92 of an acquisitionsignal detector 94. The output signal from the acquisition detector 94may be applied to the coil of the relay 50 by way of a suitableconventional relay driver circuit 104 and indicates when the scanningbeam is within the field of view of sight optics 69.

In operation, the operator aims the sighting device 12 at the tank 26 bysighting through the optical sight 66. By placing the intersection ofthe cross hairs on the tank 26, the operator establishes a line of sightfrom the optical sighting device 12 to the tank 26. The light detector68 is collimated with the optical sight 66 such that the optical centerof the light detector 68 is coincident with the optical line of sight.

The scan signal generator is then energized and applies scanning signalsto the yaw and pitch motors 46 and 48 by way of the normally closedcontacts of the relay 50. The Y SCAN and P SCAN signals cause thereflector 44 to be driven in a predetermined manner, thus causing thelaser beam to scan a predetermined area in azmuth and elevation. As thelaser beam scans across the target 26, the reflected energy from thelaser beam will strike the detector 68, thus generating error signalswhich are applied to the yaw and pitch channels 65 and 67, respectively,and to the acquisition detector 94. The output signal from theacquisition detector 94 is applied to the relay drive circuit 104 whichenergizes the relay 50, to disconnect the scan signal generator and toplace the positioning system in the track mode.

Once in the track mode, the system operates as a closed loop trackingsystem. The laser energy reflected from the target 26 which strikes thedetector 68 will provide output signals proportional to the intensityand position of the energy detected by the detector. The HI, LO, RIGHTand LEFT signals from the detector 68 are applied to the appropriate oneof the pitch and yaw channels 65 and 67.

The high gain, low noise pitch amplifiers 74 amplify the HI and LOsignals from the detector 68 by an equal amplification factor controlledby the automatic gain control circuit 82, which receives the signalsfrom all four of the amplifiers. The output signals of the pitch and yawamplifiers are summed and processed in the AGC circuit 82 to produce adc. voltage which is compared with a predetermined reference voltage.The difference signal is used to control the gain of the pitch and yawamplifiers so that the combined energy is a constant.

The normalized HI and LO signals are then applied to the differentialamplifier 80 to produce the pitch error signal P ERR:

P ERR HI (Normalized) LO (Normalized) 1. The P ERR signal may then beapplied to the phase demodulator 88 which is gated by the output signalfrom the reference photodetector 42. The phase demodulator 88 processesthe received signals at the same rate as the transmitted energy ischopped by the interrupter apparatus 34, thereby acting as a highlyselective filter and excluding any spurious noise and background signalsdetected by the detector 68 outside this time period. The low passfilter 90 smooths the P ERR signal from the phase demodulator 88,removing the high frequency components therefrom.

The smoothed P ERR signal is then applied to both the integrator 98 andthe inverter 102, and the output signals therefrom summed in the summingamplifier and applied, together with signals from the gyroscope 73 andthe pitch position sensor 79, to the pitch control motor 48 to drive thepitch control motor in a direction tending to reduce the P ERR signal tozero.

The inverter 102 inverts the filtered P ERR signal to provide a drivesignal of the same polarity as the in tegrator 98 signal. For example,assuming that the HI signal exceeds the LO signal, the output signal ofthe filter 90 will be positive. Since this positive signal is indicativeof the fact that the energy detected in the upper half of the detector68 is greater than the energy detected in the lower half, the reflector44 must be rotated in a direction to lower the laser beam in elevationto eliminate this error.

The inverter 102 is necessary because the integrator 98 inverts thesignal and the control signal component from the inverter 102 must havethe same directional control as the control signal component from theintegrator 98.

The integrator 98 is provided to eliminate residual error signals whichdo not have sufficient instantaneous amplitude to cause rotation of thepitch control motor 48 to change the position of the reflector 44. Byintegrating these residual error signals, the effect of these signals issummed over a period of time, thereby providing a large enough signal toeliminate the residual errors.

After the system has automatically changed to the track mode and isoperating as a closed loop system, the laser beam automatically tracksthe target as seen by the operator. This feature is particularlyimportant, for example, when utilizing the system for surgical purposeswhere the surgeon operating the system may increase the output power ofthe laser 30 several orders of magnitude, or may alternatively switch ona high power laser aligned with the beam of the laser 30, to perform adesired surgical function. In this way, an extremely delicate andaccurate operation may be performed on a patient by first tracking andselecting the spot with a low power laser 30. When the surgeon desiresto make a cut, the high power laser 120 may be switched on to performthe operation and then switched off when the operation is completed. Inthis manner, extreme accuracy may be obtained without the risk ofmisalignment of the high powered laser.

Referring now to FIG. 4 where a second embodiment of the presentinvention utilizing a pulsed laser as the laser illuminator isillustrated and where like numerical designations have been utilizedwhere applicable to facilitate an understanding of the invention, aconventional pulsed laser 122 which provides a narrow laser beam 124 ofshort duration, high intensity, highly directive light is provided inthe laser illuminator assembly 10. The beam 124 from the laser 122 maybe directed onto a totally reflective mirror surface 126 which directsthe beam 124 onto a totally reflective, gimbal mounted mirror surface44. The yaw and pitch angles of the mirror 44 are controlled by therespective yaw and pitch control motors 46 and 48 in response to YAW andPITCH control signals to direct the beam 124 onto the target 26 aspreviously described.

The sighting device 66 may be aimed at target 26 and the reflected laserbeam detected by the light detector 68 as previously described. Thesignals generated by the A, B, C, and D quadrants of the detector 68 maybe applied to signal amplifiers 128 and the amplified signals applied tothe input terminals 123, 125, 127 and 129 of the pulse processor 134which may include a suitable conventional circuit described infra inconnection with FIG. to control the gain of the input signals from theamplifiers 128 by an equal amount related to the sum of all of the inputsignals as previously described in connection with FIG. 3. The P ER andY ERR signals may then be applied to the input terminals 258 and 248 ofa radio transmitter 130 or other suitable conventional communicationslink to transmit the signals to the receiver 132 in the laserilluminator assembly 10. An acquisition detector 94 receives the foursignals and generates an ACQUISITION signal which is also applied to thetransmitter 130 via an input terminal 249.

The radio receiver 132 in the laser illuminator assembly receives thetransmitted signals and applies the P ERR and Y ERR signals to thenormally open contacts 116 of the mode select relay 50. The ACQUISITIONsignal is applied to a relay driver circuit 104 for operation of themode select relay 50.

As previously described, the Y ER and P ERR signals are applied to theinput terminals 59 and 63, respectively, of the summing amplifiers 58and 64 by way of the respective normally open terminals 57 and 61 of themode select relay 50 when the relay 50 is energized. When the relay 50is deenergized, Y SCAN and P SCAN signals are applied to the respectiveinput terminals 59 and 63 from the scan signal generator 54 aspreviously described. In addition, the output signals from thegyroscopes 75 and 73 and the position sensors 85 and 79 are applied tothe respective input terminals of the summing amplifiers 58 and 64 toproduce the YAW and PITCH signals applied to the yaw control motor 46and the pitch control motor 48, as previously described.

The lens 77 of the detector is utilized to defocus and thus enlarge thespot of light incident on the detector 68 so that signals related to theintensity of each quadrant of the detector will be generated when thetarget is boresighted. The availability of four quadrant signals permitsthe proportional control hereinafter described.

As previously described, the output pulses from the A, B, C, and Dquadrants of the detector 68, hereinafter referred to as the A, B, C,and D signals, are processed so that the analog error signals may betransmitted to the receiver 132 and applied therefrom to the inputterminals 116 of the mode select relay 50. The pulse processor 134 maycontain a signal control circuit of the type illustrated in FIG. 5.

The pulse processor 134 of the embodiment of FIG. 4 will now bedescribed with reference to FIGS. 5 and 6 wherein the terminalscorresponding to those illustrated in FIG. 4 have been given likenumerical designations.

With reference now to FIG. 5, the four signals A, B, C, and D areapplied respectively to the input terminals 123, 125, 127 and 129. Thesesignals are delayed respectively in delay lines 265268 and appliedrespectively to sample and hold circuits 269 272. The output terminals136 142 of the sample and hold circuits 269 272 are directly connectedto the like numbered terminals of the normalizer circuits illustrated inFIG. 6. The output signals of the sample and hold circuits are alsoapplied to a suitable conventional pulse AGC integrator 273 whose outputsignal is applied to terminal 193 of the signal amplifiers 128 of FIG.4.

The input signals A, B, C, and D are also applied to a pulse logiccircuit 274 which supplies normalizer gating signals to the inputterminal 194 of the normalizer of FIG. 6 and to the sample and holdcircuits 269 272 to reset the voltage levels associated with thepreceding pulse.

In operation, the input signals A, B, C, and D are delayed sufficientlyin the delay lines 265 268 to permit the pulse logic circuit 274 toevaluate the signals individually with respect to criteria such as pulserepetition rate, pulse width, and pulse amplitude. If the signals arefound acceptable, a gating signal is supplied to the sample and holdcircuits 269 272 which sample the signals and apply the samples to theterminals 136 142 of the normalizer of FIG. 6.

In addition, the gating signal is applied via terminal 194 to preparethe normalizer of FIG. 6 to receive the video samples.

The sampled signals are integrated in the pulse AGC integrator 273 andthe sum applied by way of terminal 193 to the signal amplifiers 128 toadjust the gain thereof in a conventional manner.

With reference to FIG. 6, the output terminals 136 142 are directlyconnected to the drain electrode of an associated one of four fieldeffect transistors 146 152. The source electrodes of the field effecttransistors 146 152 are connected to input terminals 162 168 ofconventional high input impedance amplifiers 176 by way of equalresistors 154 160. Each of the input terminals 162 168 of the respectiveamplifiers 170 176 is connected to ground through an associated one ofthe capacitors 178 184 and is additionally connected to the drainelectrodes of associated field effect transistors 186 192, the sourceelectrodes of which are grounded. The gate electrodes of each of thefield effect transistors 186 192 are connected to an input terminal 194from the pulse logic circuit of FIG. 5.

The output signals from the amplifiers 170 176 may be applied to a firstinput terminal 196 of a conventional differential amplifier 198 by wayof equal resistors 200 206, respectively. A d.c. reference voltagesource may be connected to a second input terminal 208 of the amplifier198 by way of a resistor 210. The input terminal 208 is connected to theanode electrode of a semi-conductor diode 212 by way of a resistor 214and an output terminal 216 of the amplifier 198 is connected to thecathode of the diode 212. The output terminal 216 of the amplifier 198is connected to the gate electrodes of the field effect transistors 146152 by way of one of the resistors 218 224.

The output signal from the amplifier 170 may also be applied to an inputterminal 226 of a conventional summing amplifier 228 by way of aresistor 230 and may also be applied to an input terminal 232 of aconventional summing amplifier 234 by way of a resistor 236. The inputterminals 226 and 232 of the amplifiers 228 and 234, respectively. maybe connected to ground through respective resistors 238 and 240.

The output signal from the amplifier 172 may also be applied to theinput terminal 226 of the amplifier 228 by way of a resistor 242 and toan input terminal 244 of the amplifier 234 by way of a resistor 246. Theinput terminal 244 of the amplifier 234 may be connected to an outputterminal 248 of the amplifier 234 by way of a resistor 250.

The output signal from the amplifier 174 may be applied to an inputterminal 252 of the amplifier 228 by way of a resistor 254 and to theinput terminal 244 of the amplifier 234 by way of a resistor 256. Theinput terminal 252 of the amplifier 228 may be connected to an outputterminal 258 of the amplifier 228 by way of a resistor 260.

The output signal from the amplifier 176 may be applied to the inputterminal 252 of the amplifier 228 by way of a resistor 262 and to theinput terminal 232 of the amplifier 234 by way of a resistor 264. Theoutput terminals 258 and 248 of the amplifiers 228 and 234 may beconnected to the transmitter 130 of FIG. 4.

In operation, the input signals A D are generated as previouslydescribed by the detector 68 of FIG. 4, amplified in the signalamplifiers 128, and are applied, respectively, to the drain electrodesof the field effect transistors 146 152. Since the field effecttransistors 186 192 are in a non-conducting state and the capacitors 178184 are completely discharged, the signal applied to the input terminal196 of the amplifier 198 is initially zero. Thus, the reference voltageapplied to the input terminal 208 of the amplifier 198 causes a positivevoltage to be applied to the gate electrodes of the field effecttransistors 146 152, thereby allowing the signals A, B, C, and D to bepassed to the input terminals 162 168, respectively, of the amplifiers170 176. The capacitors 178 184 thus begin to charge toward the inputsignal levels applied thereto at a rate determined by the values of theresistors 154 160 and the capacitors 178 184, i.e., the RC. timeconstants of the input circuits.

The output signals from the amplifiers 170 176 increase in a positivedirection in response to the charge on the respective capacitors 178 184until the sum of the output signals applied to the input terminal 196 ofthe amplifier 198 is equal to the reference voltage, at which time theoutput signal from the amplifier 198 switches to a negative value andcuts off the field effected transistors 146 152. The feedback pathprovided by the diode 212 and the resistor 214 feeds a portion of thenegative output signal from the amplifier 198 to the input terminal 208to prevent the output signal from the amplifier 198 from going positive.

Thus, the A, B, C, and D input signals are applied to the capacitors 178184 until the sum of the output signals from the amplifiers 170 176 isequal in amplitude to the reference voltage applied to the amplifier198. The sum E of the output voltages from the amplifiers 170 176 may,where K is amplifier gain, be expressed as:

E=KA+KB+KC+KD 2. While K may vary from pulse to pulse, it is constant inall channels.

Since the charging of the capacitors 178 184 is ef- 6 fectivelycontrolled by the sum of the output signals of the amplifiers 176, theoutput signals of the am- PEER: A+B+0+T Likewise, the normalized outputsignals A and D may be applied to one input terminal 232 of theamplifier 234 and the normalized signals B and C may be applied to theother input terminal 244 of the amplifier 234 to provide a normalizedyaw error signal Y ERR at the output terminal 248 of the amplifier 234:

YERR: A+B+C+D It is apparent from the above description that the pulseprocessor 134 operates as a resettable sample and hold circuit whichsamples the input signals A, B, C, and D for a period of time determinedby the sum of the input signals A, B, C, and D. In this manner, the A,B, C, and D signals are normalized and applied to a summing amplifier toprovide the desired P ERR and Y ERR signals. The sampling operation maybe repeated at a predetermined repetition rate by applying to the inputterminal 194 a positive pulse of sufficient duration and amplitude todrive the field effect transistors 186 192 into saturation for a periodof time sufficient to completely discharge the capacitors 178 184.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is, therefore, to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are, therefore, intended to be embracedtherein.

What is claimed is:

1. Apparatus for remotely positioning a laser device comprising:

illuminating means for illuminating a remote target with a beam ofradiant energy;

optical sighting means remote from said illuminating means and from saidtarget for establishing an optical line of sight to said target;

radiant energy detecting means carried by said optical sighting meansfor detecting radiant energy from said illuminating means reflected bysaid target and for generating error signals related to the relativepositions of said optical line of sight and the detected radiant energy;and

positioning means responsive to said error signals for lll wherein saidpositioning means is carried by said illuminating means.

3. The apparatus of claim 2 further including scan signal generatingmeans operatively connected to said positioning means for selectivelyvarying the propagation direction of the radiant energy from said lasermeans in a predetermined cyclic manner.

4. The apparatus of claim 2 further including gyroscope means carried bysaid positioning means for generating vibration error signals, saidgyroscope means being operatively connected to said positioning means toreduce laser means vibration induced variation in the propagationdirection of the radiant energy from said laser beam.

5. The apparatus of claim 4 wherein said laser means includes lasermeans for selectively generating a second beam of radiant energycoincident with the beam from said first-mentioned laser means, theradiant energy of said second laser means being at least an order ofmagnitude greater than the radiant energy of said first-mentioned lasermeans.

6. The apparatus of claim 2 wherein said laser means includes means forselectively generating a second beam of radiant energy coincident withthe beam from said first mentioned laser means, the radiant energy ofsaid second laser means being at least an order of magnitude greaterthan the radiant energy of said first mentioned laser means.

7. The apparatus of claim 6 further including gyroscope means carried bysaid laser means for generating vibration error signals, said gyroscopemeans being operatively connected to said positioning means to reducelaser means induced variation in the propagation direction of theradiant energy from said laser means.

8. Laser target illuminating apparatus comprising:

a laser;

means for modifying the direction of propagation of the radiant energyfrom said laser in a predetermined cyclical manner;

a remote control device for optically viewing the target, said devicehaving a radiant energy detector aligned therewith for generating anerror signal related to the relative positions of the detected energyand said detector;

means for modifying the direction of propagation of the radiant energyfrom said laser responsively to said error signal; and

means for selectively connecting said laser to one of said propagationdirection modifying means.

9. The apparatus of claim 8 including: a second laser aligned with saidfirst mentioned laser, the radiant energy from said second laser beingat least an order of magnitude greater than the radiant energy from saidfirst mentioned laser; and means for selectively energizing said secondlaser.

10. Portable apparatus for remotely positioning an illuminating devicecomprising:

optical sighting means remote from the illuminating device and from atarget illuminated by the illu minating device for establishing anoptical line of sight to the target;

radiant energy detecting means carried by said optical sighting meansfor detecting radiant energy from the illuminating device reflected bythe tar- 12 4 get, and for generating error signals related to therelative positions of said optical line of sight and the detectedradiant energy; and

positioning means responsive to said error signals and carried by theilluminating device for varying the propagation direction of the radiantenergy from the illuminating device.

11. Portable apparatus for designating a target to a remote source ofradiant energy comprising:

optical sighting means;

a detector of radiant energy boresighted with said optical sightingmeans for producing an error signal related to the position of thedetected radiant energy relative to the axis of said optical sightingmeans; and

transmitting means for transmitting said error signals to the remotesource of radiant energy.

12. The apparatus of claim 11 including handle means adapted to begrasped by a human hand and an optical filter for increasing thesensitivity of said detector to the frequency of the energy from theremote source of radiant energy.

13. The apparatus of claim 12 wherein the illuminating device is a laserand wherein the mass of said sighting means is smaller than the mass ofthe laser device.

14. A method of designating a remote target to be illuminated by a lasercomprising the steps of:

a. generating a laser beam;

b. modifying the direction of propagation of the laser beam in apredetermined manner;

c. focusing a radiant energy detector on the target to be illuminated;

d. detecting the reflected radiant energy of the laser beam in the fieldof view of the detector; and

e. thereafter modifying the direction of propagation of the laser beamresponsively to the position of the detected reflected radiant energyrelative to the detector.

15. The method of claim 14 further including the step of increasing byat least one order of magnitude the power of the laser upon substantialcentering of the detected energy in the field of the detector.

16. A method of designating a remote target to a remote source ofradiant energy comprising the steps of:

a. optically acquiring the remote target thereby centering a radiantenergy detector on the target;

b. detecting radiant energy from the remote source in the field of viewof the target;

c. generating error signals related to the position of the detectedradiant energy relative to the center of the detector; and

d. transmitting the error signals to the remote source whereby thesource may be positioned to reduce the error signals.

17. A method of performing surgery comprising the steps of:

a. focusing a radiant energy detector on the tissue to be cut;

b. scanning a beam of radiant energy over tissue in the area of thetissue to be cut until detected in the field of view of the detector,said radiant energy being insufficient to cut the tissue;

c. aligning the beam of radiant energy with the detector; and

1 cal attenuator.

19. The method of claim 17 wherein the radiant energy of the beam isincreased by the energization of a laser aligned with the firstmentioned beam of radiant 17 wherein the radiant 5 y-

1. Apparatus for remotely positioning a laser device comprising:illuminating means for illuminating a remote target with a beam ofradiant energy; optical sighting means remote from said illuminatingmeans and from said target for establishing an optical line of sight tosaid target; radiant energy detecting means carried by said opticalsighting means for detecting radiant energy from said illuminating meansreflected by said target and for generating error signals related to therelative positions of said optical line of sight and the detectedradiant energy; and positioning means responsive to said error signalsfor varying the propagation direction of the radiant energy from saidilluminating means.
 2. The apparatus of claim 1 wherein saidilluminating means is a laser; wherein the mass of said sighting meansis smaller than the mass of said laser means; and wherein saidpositioning means is carried by said illuminating means.
 3. Theapparatus of claim 2 further including scan signal generating meansoperatively connected to said positioning means for selectively varyingthe propagation direction of the radiant energy from said laser means ina predetermined cyclic manner.
 4. The apparatus of claim 2 furtherincluding gyroscope means carried by said positioning means forgenerating vibration error signals, said gyroscope means beingoperatively connected to said positioning means to reduce laser meansvibration induced variation in the propagation direction of the radiantenergy from said laser beam.
 5. The apparatus of claim 4 wherein saidlaser means includes laser means for selectively generating a secondbeam of radiant energy coincident with the beam from saidfirst-mentioned laser means, the radiant energy of said second lasermeans being at least an order of magnitude greater than the radiantenergy of said first-mentioned laser means.
 6. The apparatus of claim 2wherein said laser means includes means for selectively generating asecond beam of radiant energy coincident with the beam from said firstmentioned laser means, the radiant energy of said second laser meansbeing at least an order of magnitude greater than the radiant energy ofsaid first mentioned laser means.
 7. The apparatus of claim 6 furtherincluding gyroscope means carried by said laser means for generatingvibration error signals, said gyroscope means being operativelyconnected to said positioning means to reduce laser means inducedvariation in the propagation direction of the radiant energy from saidlaser means.
 8. Laser target illuminating apparatus comprising: a laser;means for modifying the direction of propagation of the radiant energyfrom said laser in a predetermined cyclical manner; a remote controldevice for optically viewing the target, said device having a radiantenergy detector aligned therewith for generating an error signal relatedto the relative positions of the detected energy and said detector;means for modifyiNg the direction of propagation of the radiant energyfrom said laser responsively to said error signal; and means forselectively connecting said laser to one of said propagation directionmodifying means.
 9. The apparatus of claim 8 including: a second laseraligned with said first mentioned laser, the radiant energy from saidsecond laser being at least an order of magnitude greater than theradiant energy from said first mentioned laser; and means forselectively energizing said second laser.
 10. Portable apparatus forremotely positioning an illuminating device comprising: optical sightingmeans remote from the illuminating device and from a target illuminatedby the illuminating device for establishing an optical line of sight tothe target; radiant energy detecting means carried by said opticalsighting means for detecting radiant energy from the illuminating devicereflected by the target, and for generating error signals related to therelative positions of said optical line of sight and the detectedradiant energy; and positioning means responsive to said error signalsand carried by the illuminating device for varying the propagationdirection of the radiant energy from the illuminating device. 11.Portable apparatus for designating a target to a remote source ofradiant energy comprising: optical sighting means; a detector of radiantenergy boresighted with said optical sighting means for producing anerror signal related to the position of the detected radiant energyrelative to the axis of said optical sighting means; and transmittingmeans for transmitting said error signals to the remote source ofradiant energy.
 12. The apparatus of claim 11 including handle meansadapted to be grasped by a human hand and an optical filter forincreasing the sensitivity of said detector to the frequency of theenergy from the remote source of radiant energy.
 13. The apparatus ofclaim 12 wherein the illuminating device is a laser and wherein the massof said sighting means is smaller than the mass of the laser device. 14.A method of designating a remote target to be illuminated by a lasercomprising the steps of: a. generating a laser beam; b. modifying thedirection of propagation of the laser beam in a predetermined manner; c.focusing a radiant energy detector on the target to be illuminated; d.detecting the reflected radiant energy of the laser beam in the field ofview of the detector; and e. thereafter modifying the direction ofpropagation of the laser beam responsively to the position of thedetected reflected radiant energy relative to the detector.
 15. Themethod of claim 14 further including the step of increasing by at leastone order of magnitude the power of the laser upon substantial centeringof the detected energy in the field of the detector.
 16. A method ofdesignating a remote target to a remote source of radiant energycomprising the steps of: a. optically acquiring the remote targetthereby centering a radiant energy detector on the target; b. detectingradiant energy from the remote source in the field of view of thetarget; c. generating error signals related to the position of thedetected radiant energy relative to the center of the detector; and d.transmitting the error signals to the remote source whereby the sourcemay be positioned to reduce the error signals.
 17. A method ofperforming surgery comprising the steps of: a. focusing a radiant energydetector on the tissue to be cut; b. scanning a beam of radiant energyover tissue in the area of the tissue to be cut until detected in thefield of view of the detector, said radiant energy being insufficient tocut the tissue; c. aligning the beam of radiant energy with thedetector; and d. increasing the radiant energy of the beam sufficientlyto cut the tissue whereby inadvertent damage to tissue due to improperpositioning of the laser is avoided.
 18. The method of Claim 17 whereinthe radiant energy of the beam is increased by removal of an opticalattenuator.
 19. The method of claim 17 wherein the radiant energy of thebeam is increased by the energization of a laser aligned with the firstmentioned beam of radiant energy.